The present invention is directed to a production run separation control for a stacker conveyor. In particular, the invention is directed to a control for creating a separation between the box blanks of an old production run and the box blanks of a succeeding or new production run on the stacker conveyor. This is accomplished by automatically retarding the movement of the first full size box blank of the new production run on the stacker conveyor as the box blanks of the old production run are cleared by the stacker conveyor.
Various techniques are known for clearing the box blanks of an old production run off a conveyor. For example, in U.S. Pat. No. 3,791,269, a sheet delivery device includes a counter which counts the number of sheets in a production run. When a predetermined count is reached, denoting the end of the production run, the counter activates a piston to lower a conveyor with respect to a bank of suction devices. The devices hold the first sheets of the new production run while the old run is cleared on the conveyor.
Similarly, in U.S. Pat. No. 3,880,420, the speed of a corrugator is related by a predetermined ratio to the speeds of a side take-off conveyor, a transfer conveyor and stacker conveyor. A change in speed of the side take-off, transfer and stacker conveyors owing to a change of the corrugator speed during an order changeover is delayed to permit the clearing of all old order sheets on the side take-off conveyor. The delay is effected by electrical or pneumatic means.
A further example is shown in U.S. Pat. No. 3,178,174 in which a suction chamber is provided at the inlet of a shingling conveyor belt to pull down the rear end of a sheet to separate it from a following sheet.
A gap type corrugator is disclosed in copending U.S. patent application Ser. No. 903,350 entitled Continuous Running Corrugator, filed May 5, 1978 and assigned to the assignee of the instant application. That application describes a method of creating a gap in the severed web to provide an interval for the slitter-scorer and cut-off machines to be readjusted for the next production run. In contrast to this gap type corrugator, the instant application is directed to a method of and apparatus for separating the sheets from two production runs without varying the speed of the cut-off machine.
There is presently a need in the industry for an order separation control which automatically creates the separation between old and new production runs on the stacker conveyor by tracking the edges of the web severed during a change-over in production runs.